Okay. Let’s see.

I tell the airlock to repressurize. It refuses—the outer door is open. Nice to know that safety interlock is there, but I’ll have to work around it.

It’s not hard—there’s a manual relief valve that will just let air from the ship into the airlock. It bypasses all computer controls. You don’t want someone to die because of a software malfunction, right?

I open the relief valve. Air rushes in from the Hail Mary and, with the airlock wide open, into the tunnel. Within three minutes, the airflow slows and then stops. My suit readings tell me there’s 400 hectopascals of pressure outside. The Hail Mary has equalized with my part of the tunnel.

I close the relief valve and wait. I watch the external pressure gauge on my EVA suit. The pressure stays put at 400 hectopascals. We have a good seal.

Eridians know how to glue xenonite to aluminum. Of course they do. Aluminum’s an element, and any species that could invent xenonite in the first place must know their way around the periodic table a thousand times better than we do.

Time for a leap of faith. I pop the seals of the EVA suit and climb out the back. The strong smell of ammonia permeates the air but it’s otherwise breathable. It’s my own air supply, after all. I push the EVA suit back toward the airlock. The helmet lamps are my only source of light, so I finagle the suit so the lights stay pointed down the tunnel.

I float over to the mystery wall and reach out to touch it, but stop short. I can feel the heat even from a few inches away. Eridians like it hot.

In fact, I’m starting to sweat. The tunnel walls are heating up my air. It’s uncomfortable, but not too bad. I can open the Hail Mary’s inner airlock door if I want my climate control to take over. Then our life-support systems can fight it out. They’ll keep the hot side hot and I’ll keep the cold side cold.

Even with the sweat forming on my brow and the strong ammonia odor making my eyes water, I press on. I’m just too curious not to. Could anyone blame me?

There are at least twenty little hexagons on this wall. They’re all different colors and textures and I think a couple of them might be translucent. I should catalog each one and figure out if I can identify what they’re made of. Looking closer, I see there’s a definite seam running along the edges of the hexes.

That’s when I hear a sound come from the other side:

Knock, knock, knock.

They knocked, so it’s only polite for me to knock back. I know that wall is going to be hot, so I rap my knuckles on it as fast as I can.

I knock three times, just like they did.

There’s no immediate response. I take a good long look at the hex wall. There are forty hexes, I’d say, and each one seems to be unique. Different materials, maybe? I feel like I’m supposed to do something here, but what?

Are they watching me? I don’t see anything that looks like a camera.

I hold up my finger and point back to my airlock. I don’t know if they can see me or if they have any idea what that hand gesture means. I kick off the hex wall and back to the airlock, and then I open the inner door. Why not? The pressure is the same on both sides. It’s okay to leave the airlock open. If there’s a pressure loss in that tunnel, the air leaving the ship will slam the inner airlock door shut and I’ll get to stay alive.

I go to the lab and pack a bag with a few choice items, then return to the tunnel.

First I tape LED lamps to various spots along the tunnel and aim them at the hex wall. Now I can see what I’m doing, at least. I pull out my trusty handheld x-ray spectrometer and scan one of the hexes. It’s xenonite. Almost the same composition as the cylinders they sent me earlier.

Almost.

There are a few differences in the trace elements. Interesting. Maybe xenonite is like steel—lots of different recipes? I check the next hex over. Another slightly unique combination.

Best guess: Different types of xenonite are optimal for different situations. They had no idea what my air was like. So they want to test various compounds against it. When I leave the tunnel, they’ll inspect the hexes to decide which one fares best.

That means I should leave the tunnel. Should I depressurize my side for them? Seems polite. I could easily do it—I’d just tell the airlock to cycle. It would think, “Golly, there sure is a lot of air in me today!” but would just keep pumping until there was a vacuum.

But then again, maybe they have a way of sampling the air on this side. If so, I should leave it here, right?

I decide to leave it be. They probably have a sampling technique. If I were making this tunnel, that’s what I’d do, and they seem pretty bright.

I turn back toward the airlock, but something catches my eye. Movement!

I shoot my attention back to the hex wall. Nothing’s changed. But I could swear I saw something move. Some of the hexes are shiny—I probably caught a glimpse of my reflection.

Wait…

One hex stands out. Why?

It’s near the tunnel wall. Not very obvious. I float over to take a closer look.

“Holy cow!” I say.

This hex is clear! All the others are opaque, but this one is like glass! I pull one of the lamps off the wall and hold it up to the hex. I press my head against the hot wall to get a closer look.

Light gets through into the other side. I can see the tunnel walls beyond. Either their side is a vacuum or their air is clear. Either way, there’s nothing blocking or dulling my view.

Suddenly, a rock hits the other side of the hex. It stays there. It’s just a few inches away from me. It’s roughly triangular, kind of a dark brown, and has rough, jagged edges. Like you might see on the tip of a spear from a caveman.

Have I met spacefaring cavemen?

Stop being stupid, Ryland.

Why did they put a rock there? And is it sticky? Are they trying to block my view? If so, they’re doing a terrible job. The little triangle is only a couple of inches wide at the thickest point and the hex is a good 8 inches across.

And it gets sillier. Now the rock is bending at articulated joints, and there are two similar rocks that do the same thing, and there’s a longer rock attached to them that—

That’s not a rock. It’s a claw! It’s a claw with three fingers!

I’m desperate to see more! I press my face against the hex. It burns, but I resist the urge to pull away. There’s pain, yes, and it’s probably going to leave a mark. I should go back to the lab and find a camera, but come on. No one would have that presence of mind at a time like this.

I groan as my face aches, but I’m rewarded with a better view.